$(function () {
    $('#skin a').click(function () {
        $("#" + this.id).addClass("selected").siblings().removeClass("selected");
        $('#skinCss').attr("href", "css/" + (this.id) + "/easyui.css");
    });
})
	// The second line`s effect is finding the Dom tree "li".
	// The third line:add selected.
	// The forth line:change css.